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/*
* This file is subject to the terms and conditions of the GNU General Public
* License. See the file "COPYING" in the main directory of this archive
* for more details.
*
* Copyright (C) 2007 MIPS Technologies, Inc.
* Copyright (C) 2007 Ralf Baechle <ralf@linux-mips.org>
*/
#include <linux/clockchips.h>
#include <linux/interrupt.h>
#include <linux/percpu.h>
#include <linux/smp.h>
#include <asm/smtc_ipi.h>
#include <asm/time.h>
#include <asm/cevt-r4k.h>
/*
* The SMTC Kernel for the 34K, 1004K, et. al. replaces several
* of these routines with SMTC-specific variants.
*/
#ifndef CONFIG_MIPS_MT_SMTC
static int mips_next_event(unsigned long delta,
struct clock_event_device *evt)
{
unsigned int cnt;
int res;
cnt = read_c0_count();
cnt += delta;
write_c0_compare(cnt);
res = ((int)(read_c0_count() - cnt) > 0) ? -ETIME : 0;
return res;
}
#endif /* CONFIG_MIPS_MT_SMTC */
void mips_set_clock_mode(enum clock_event_mode mode,
struct clock_event_device *evt)
{
/* Nothing to do ... */
}
DEFINE_PER_CPU(struct clock_event_device, mips_clockevent_device);
int cp0_timer_irq_installed;
#ifndef CONFIG_MIPS_MT_SMTC
irqreturn_t c0_compare_interrupt(int irq, void *dev_id)
{
const int r2 = cpu_has_mips_r2;
struct clock_event_device *cd;
int cpu = smp_processor_id();
/*
* Suckage alert:
* Before R2 of the architecture there was no way to see if a
* performance counter interrupt was pending, so we have to run
* the performance counter interrupt handler anyway.
*/
if (handle_perf_irq(r2))
goto out;
/*
* The same applies to performance counter interrupts. But with the
* above we now know that the reason we got here must be a timer
* interrupt. Being the paranoiacs we are we check anyway.
*/
if (!r2 || (read_c0_cause() & (1 << 30))) {
/* Clear Count/Compare Interrupt */
write_c0_compare(read_c0_compare());
cd = &per_cpu(mips_clockevent_device, cpu);
cd->event_handler(cd);
}
out:
return IRQ_HANDLED;
}
#endif /* Not CONFIG_MIPS_MT_SMTC */
struct irqaction c0_compare_irqaction = {
.handler = c0_compare_interrupt,
.flags = IRQF_DISABLED | IRQF_PERCPU,
.name = "timer",
};
void mips_event_handler(struct clock_event_device *dev)
{
}
/*
* FIXME: This doesn't hold for the relocated E9000 compare interrupt.
*/
static int c0_compare_int_pending(void)
{
return (read_c0_cause() >> cp0_compare_irq) & 0x100;
}
/*
* Compare interrupt can be routed and latched outside the core,
* so a single execution hazard barrier may not be enough to give
* it time to clear as seen in the Cause register. 4 time the
* pipeline depth seems reasonably conservative, and empirically
* works better in configurations with high CPU/bus clock ratios.
*/
#define compare_change_hazard() \
do { \
irq_disable_hazard(); \
irq_disable_hazard(); \
irq_disable_hazard(); \
irq_disable_hazard(); \
} while (0)
int c0_compare_int_usable(void)
{
unsigned int delta;
unsigned int cnt;
/*
* IP7 already pending? Try to clear it by acking the timer.
*/
if (c0_compare_int_pending()) {
write_c0_compare(read_c0_count());
compare_change_hazard();
if (c0_compare_int_pending())
return 0;
}
for (delta = 0x10; delta <= 0x400000; delta <<= 1) {
cnt = read_c0_count();
cnt += delta;
write_c0_compare(cnt);
compare_change_hazard();
if ((int)(read_c0_count() - cnt) < 0)
break;
/* increase delta if the timer was already expired */
}
while ((int)(read_c0_count() - cnt) <= 0)
; /* Wait for expiry */
compare_change_hazard();
if (!c0_compare_int_pending())
return 0;
write_c0_compare(read_c0_count());
compare_change_hazard();
if (c0_compare_int_pending())
return 0;
/*
* Feels like a real count / compare timer.
*/
return 1;
}
#ifndef CONFIG_MIPS_MT_SMTC
int __cpuinit r4k_clockevent_init(void)
{
uint64_t mips_freq = mips_hpt_frequency;
unsigned int cpu = smp_processor_id();
struct clock_event_device *cd;
unsigned int irq;
if (!cpu_has_counter || !mips_hpt_frequency)
return -ENXIO;
if (!c0_compare_int_usable())
return -ENXIO;
/*
* With vectored interrupts things are getting platform specific.
* get_c0_compare_int is a hook to allow a platform to return the
* interrupt number of it's liking.
*/
irq = MIPS_CPU_IRQ_BASE + cp0_compare_irq;
if (get_c0_compare_int)
irq = get_c0_compare_int();
cd = &per_cpu(mips_clockevent_device, cpu);
cd->name = "MIPS";
cd->features = CLOCK_EVT_FEAT_ONESHOT;
/* Calculate the min / max delta */
cd->mult = div_sc((unsigned long) mips_freq, NSEC_PER_SEC, 32);
cd->shift = 32;
cd->max_delta_ns = clockevent_delta2ns(0x7fffffff, cd);
cd->min_delta_ns = clockevent_delta2ns(0x300, cd);
cd->rating = 300;
cd->irq = irq;
cd->cpumask = cpumask_of(cpu);
cd->set_next_event = mips_next_event;
cd->set_mode = mips_set_clock_mode;
cd->event_handler = mips_event_handler;
clockevents_register_device(cd);
if (cp0_timer_irq_installed)
return 0;
cp0_timer_irq_installed = 1;
setup_irq(irq, &c0_compare_irqaction);
return 0;
}
#endif /* Not CONFIG_MIPS_MT_SMTC */
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